2006 Chevy Trailblazer cranks but no start

i recently replaced the fuel level sensor on my 06 trailblazer. I dropped the tank removed fuel pump assembly repaired the level sensor and reinstalled in in revearse order of take down. I primed the pump and the vehical started and idled fine. Went for a test drive and rpms dropped to 5k and began to idle very rough. I checked fuel psi, the gauge read 59 psi, it should read specs are 57 psi. Looked for losse connections, no leaks all plugs and hoses are secure. I attemped to start and again very rough idle. Checked codes po506 low idle indication. Replaced plugs cleaned throttle body, and now still will not start please help.